1. Field of the Invention
The present invention relates generally to touch sensing apparatuses, and particularly to a touch sensing apparatus for sensing electricity signals of an object.
2. Description of Related Art
There are several available types of touch-sensing apparatuses that may be employed for use as positional indicators in apparatus such as personal computers. Among them, resistive-membrane positioning sensors and capacitive positioning sensors are well known and typically used in several applications. However, the resistive-membrane positioning sensors generally have poor resolutions. In addition, surfaces of the resistive-membrane positioning sensors are often exposed to air, and therefore are easily worn out. Furthermore, resistive-membrane positioning sensors are relatively expensive.
A capacitive positioning sensor typically includes a substrate which supports a first and second interleaved, closely spaced, non-overlapping arrays of conductive plates. An insulating layer overlies the first and second arrays. When an outer surface of the insulating layer is touched, the capacitances of at least one of the columns of plates of the first array and one of the rows of plates of the second array underlying the insulating layer at a location being touched changes with respect to ambient ground. Based upon the measured capacitance of each column of the first array and row of the second array, a microcomputer produces output signals representing the coordinates of the location being touched. These output signals can be used, for example, to control a position of a cursor on a display screen of a personal computer or to make a selected function command. Although the capacitive positioning sensor has been designed to avoid being exposed in air and thereby to avoid being easily worn out, however, by overlying the insulating layer, the sensitivity of the touch sensing apparatus is reduced.
What is still needed is a touch sensing apparatus with reduced circuitry complexity, improved sense sensitivity, improved efficiency, and lower manufacturing costs.